Charge bonus to Saddles mod gives saddles a charge benefit that is correlated with the value of the armor. There are numerous alternatives.

As opposed to a light skirmisher horseman, expensive, fully armored cavalry is supposed to have more impact when charging against infantry.

All base saddles receive a charge bonus modifier that is connected to the armor value thanks to the mod. You should be able to determine how much charge bonus to anticipate by simply glancing at the armor value of the item.

Many saddles contain different speed/maneuverability/charge bonus modifiers in their stat descriptions, but they are typically at a value of 0. Now, these values have simply been changed or added for charge bonus.